1. Field of the Invention
The present invention relates to a heterogeneous blend of a polyolefin and a nylon/polyvinyl alcohol blend, and to articles of such blend, especially in the form of barriers to permeation of fluid, liquid and gaseous, materials.
2. Description of Related Art
Laminar articles derived from a blend of polyolefin and nylon or nylon/polyvinyl alcohol blends have been used as fuel tanks for motor vehicles, providing a barrier minimizing the diffusion of hydrocarbons and oxygenated compounds in the fuel through the walls of the tank. U.S. Pat. No. 4,410,482 describes laminar articles of a polyolefin and a condensation polymer. European Patent Application No. 0015556 describes laminar articles in which the nylon barrier resin has been replaced with polyvinyl alcohol or ethylene/vinyl alcohol copolymers.
U.S. Pat. No. 4,950,513 describes a laminar article with improved barrier properties to oxygenated and hydrocarbon compounds. The article is prepared by blending about 60 to about 97 weight percent polyolefin with a melt blend of about 2 to about 39 weight percent nylon and a polyvinyl alcohol component, and using about 0.25 to about 12 weight percent of an alkylcarboxyl-substituted polyolefin as a compatibilizer. The compatibilizer is prepared by grafting and has about 0.01 to about 20 weight percent graft monomer. The fluid barrier properties of an article made thereby are reported to be excellent, particularly in tests employing methanol/xylene mixtures.
Recent changes in emission regulations have led to the addition of ethanol to the hydrocarbon fuels. The loss of a fuel mixture of oxygenated compounds and hydrocarbons by diffusion through the walls of a container with a laminar structure of polyolefin and nylon has in general been found to be sufficiently great as to be unacceptable from an environmental standpoint. Thus there is a need for improved containers for the storage of mixtures of hydrocarbons and oxygenated compounds, such as gas tanks and cans.